Electrical mains cable sizing (Home Theater room)

hi.i plan to replace my power supply cable for DB to my hifi room. now i using 4mm normal cable buy from the electricle shop.and i plan to buy supra LoRad 3g2.5.is the 13AWG and size is 2.5mm.current NOM is 16amp but i need to know this cable it is too small for my home theater room? can any master give me advice.

It all depends on total power requirement of your HT system. A 16 amp cable APPEARS adequate but it would not be able to power your system to its optimum performance.
Ideally you should run a 63amp cable from your existing DB to your HT room to another new DB. From this new DB run smaller cables to several power sockets. Sharing power socket would not produce optimum performance from your system. It all depends on your current system, would your devices benefit from such power supply setup? A properly setup system would.

DrWho wrote:It all depends on total power requirement of your HT system. A 16 amp cable APPEARS adequate but it would not be able to power your system to its optimum performance.
Ideally you should run a 63amp cable from your existing DB to your HT room to another new DB. From this new DB run smaller cables to several power sockets. Sharing power socket would not produce optimum performance from your system. It all depends on your current system, would your devices benefit from such power supply setup? A properly setup system would.

Ya,I believe what you suggest.my friend suggest to replace the fuse for my onkyo receiver.the fuse in onkyo is 125v.3.15amp.slow blow.and i have few pcs russ andrew fuse rating is 3.15amp but is fast blow and 250volt.will cause problem for my receiver if i replace it?

Thank

I believe fuses are generally independent of voltage rating. Do not replace a slow blow with a fast blow fuse. The fuse would most probably blow at start up due to the initial rush of current.

DrWho wrote:I believe fuses are generally independent of voltage rating. Do not replace a slow blow with a fast blow fuse. The fuse would most probably blow at start up due to the initial rush of current.

Fuses carry both Amp and voltage ratings.

Amp because they are designed to blow and act as a safety device once the current exceeds its rated capability.

Voltage rating is to ensure that the fuse is not used in a situation where the voltage might breakdown the insulation of the fuse assembly in which the whole fuse would become a conductor and ceases to function as a fuse anymore.

So yes, the Voltage rating on a fuse is very important also. But one can use an over-rated voltage rating in a lower voltage situation with no problems whatsoever. (ie, if the fuse is rated to 250V, and you just use it in a 100V environment, no problem at all).

chin cp wrote:

DrWho wrote:It all depends on total power requirement of your HT system. A 16 amp cable APPEARS adequate but it would not be able to power your system to its optimum performance.
Ideally you should run a 63amp cable from your existing DB to your HT room to another new DB. From this new DB run smaller cables to several power sockets. Sharing power socket would not produce optimum performance from your system. It all depends on your current system, would your devices benefit from such power supply setup? A properly setup system would.

Ya,I believe what you suggest.my friend suggest to replace the fuse for my onkyo receiver.the fuse in onkyo is 125v.3.15amp.slow blow.and i have few pcs russ andrew fuse rating is 3.15amp but is fast blow and 250volt.will cause problem for my receiver if i replace it?

Thank

Should not be a problem.

But in case it keeps blowing (but dont worry, no harm should happen to the equipment) because the Russ Andrews is a Fast-blo, then u need to look for a equiv Slo-Blo fuse then.

Slo-Blo fuses usually have its internal filament wound as an inductor choke, so it smoothens out any small spikes and surges without breaking the filament too soon.
Fast-blo is usually just a thin hairline filament inside and intolerable to some current spikes and surges.

Thank for your good advice.

mugenfoo wrote:

DrWho wrote:I believe fuses are generally independent of voltage rating. Do not replace a slow blow with a fast blow fuse. The fuse would most probably blow at start up due to the initial rush of current.

Fuses carry both Amp and voltage ratings.

Amp because they are designed to blow and act as a safety device once the current exceeds its rated capability.

Voltage rating is to ensure that the fuse is not used in a situation where the voltage might breakdown the insulation of the fuse assembly in which the whole fuse would become a conductor and ceases to function as a fuse anymore.

So yes, the Voltage rating on a fuse is very important also. But one can use an over-rated voltage rating in a lower voltage situation with no problems whatsoever. (ie, if the fuse is rated to 250V, and you just use it in a 100V environment, no problem at all).

Voltage rating is relevant only when the voltage ratings are far apart, eg using a car fuse in a 240V audio device. This might cause arcing as mentioned by you. In an audio system 120V or 240V fuse rating are in general interchangeable and would not cause arcing. That is why his current fuse though rated at 125V is not giving him any problem.

Well, who's to say "how far apart is far? "

So if the original fuse is rated to XXX Voltage, better stick to XXX or better voltage.

Same goes for those AC cords with insulation that are rated only to 120V(ac). Carrying 240V(ac) probably wont cause much problems, but should there be a higher voltage surge, you can bet that the 120V power cord would probably melt sooner than a 240V rated power cord.

Just one of the reasons why US style power cords are not BS or AS certified for use in the UK, AUS/NZ regions.

mugenfoo wrote:Well, who's to say "how far apart is far? "

Experience! In audio equipment the fuses are interchangeable vis a vis 120V and 240V.

In cases where the equipment are rated for multivolt regions (ie, Voltage selector switches in the rear), the mfg would install the HIGHER Voltage rating fuses instead of vice-versa for reasons mentioned before.

It's simply good common sense practice to overspec the safety margins, instead of going the opposite and pushing the rated limits. If a certain deviation from original specs cannot be avoided, its better to deviate towards the safe-side than on the danger-side.

Of course if anyone feels that they can safely rely on "experience" confidently without much consequences, then do go right ahead.
But I would personally rather stick to the line of thought which is to be safe than sorry.

There is an age-old saying. "There is no fear of 10,000. But the greatest fear of 10,001".

不怕一万, 最怕万一

Hi Chin CP,

Base on what u describe, it seems that u r pulling a wire from a wall socket. I am a bit amazed that u r actually pulling wire directly from ur DB. Are you sure this is what u r doing?

If yes, u better practise some safety; whether u have make the ground properly? It need to have a RCD to govern it.

Next, u should have a MCB or Fuse to for this particular "life" line. I dont really get ur 4mm mean. Do you mean the conductor diameter? IF yes, this is seriously 1 thick wire. Generally, there is some pretty thick wire where contractor use for construction, this can be very good. much better than the 13AWG supra!. I truly suggest that u practise good caution on what u plan to do; as it can cause fire or death on the simpliest mistake.

Hi Chin, if I were u, I'll stick with ur 4mm cable . The 4mm can anytime take more current than ur supra 2.5mm. If u r keen to change to have better dedicated powerline n grounding, do talk to Adrian(Audio Image).

4mm is nominal wire for 15-20amps rating from what I remember hearing from an electrical shop when I went shopping for mains wire at one time.

noodle88 wrote:Hi Chin, if I were u, I'll stick with ur 4mm cable . The 4mm can anytime take more current than ur supra 2.5mm. If u r keen to change to have better dedicated powerline n grounding, do talk to Adrian(Audio Image).

Ya,finally i make the decision not to replace the 4mm cable.thank for all the useful advice.

Interesting photo to share...

Dat the cheepest plasticky EMKAY Rm8 socket. Like the Chinese saying, good to look at, no good to eat.

Talking about quality of main power contacts... there are a lot of really low grade stuffs out there. Even those Sirim approve one.



Some 3 pin plugs, the plastic is so thin, u can break it if u accidentally step on it. If you happen to see some of the termination inside for some of those cheapy... u can almost faint.



Darn that I am hypocrite on it, because I did use 1 of this cheapy extension cable as well. the cable becomes warm when power demand reach 1400w... haha, I am a dangerous man.

On the topic of 3-pin plugs, those available in Malaysia from hardware shop, some come as cheap as less than RM5. Dont think only about the contact, plastic and wiring, look at the supplied fuse.

Some of the fuses are just ceramic tubing with 2 caps with a thin wire inside, hold together with cheap glue, some even without damping filling to prevent fire upon the fuse element(thin wire) burnt out.

It worthwhile to go about in your home and look at the fuse inside your home appliance. Those that work in humid and damp place such as washing machine, rice cooker, kettle etc do check the fuse condition. Just buy a packet of 13A Bussmann fuses and replace those you think do not pass your own safety margin. As you go along doing that, you will also note the 3-pin plug and then decide which of the plug have reach a safety compromised position.